Electric motor

ABSTRACT

According to one embodiment, an electric motor includes a stator, a rotor, bearings and a rotor shaft, in a frame, supporting surfaces on the rotor, and a plurality of threaded holes in the frame, which are configured to receive bolts for pressing the support surfaces from outside.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of PCT Application No.PCT/JP2011/053541, filed Feb. 18, 2011 and based upon and claiming thebenefit of priority from Japanese Patent Application No. 2010-035408,filed Feb. 19, 2010, the entire contents of all of which areincorporated herein by reference.

FIELD

Embodiments described herein relate generally to an electric motor fordriving a vehicle, for example, for driving a railway vehicle.

BACKGROUND

A driving device for a vehicle, for example, a driving device for arailway vehicle includes traction electric motors provided respectivelyin a truck near wheels and a controlling device that controls thesetraction electric motors. Output shafts of the traction electric motorsare connected to the wheels via series of gears, and drive the wheels.The driving electric motor conventionally has a self-ventilation coolingstructure in which cooling is performed by flowing external air insidethereof, and bearings supporting the rotation shafts are lubricated bylubricant grease.

Since the electric motors for the railway vehicle are installed in thetrucks, there are quite a few cases in which they are exposed to foreignsubstances from outside such as dust, rain, snow, and the like. Due tothis, the electric motors require periodic maintenance that accompaniesdisassembly, and cleaning of the insides of the devices that have beencontaminated by the foreign substances from the outside is highlyrecommended.

On the other hand, needs to elongate a maintenance cycle, that is, needsfor electric motors which can reduce the number of times of maintenanceare increasing. In order to meet such needs, a development of a fullyenclosed type electric motor is under progress.

Each of such electric motors includes a stator core provided on an innercircumferential side of a cylindrical frame and having a stator coil,and a bracket and a housing attached to both sides of the frame andconfiguring a sealed casing, and a bearing is internally providedrespectively in these bracket and housing. A rotor shaft extends insidethe sealed casing, and both end portions thereof are rotatably supportedby the bearings. A rotor core is attached to a center portion of therotor shaft, and is positioned at an inner side of the stator core.Further, a partition plate is attached to each end portion of the rotorshaft inside the sealed casing, and an outer periphery of each partitionplate forms a labyrinth seal portion.

The electric motors configured as described above are the fully enclosedtype motors, and since external air does not flow inside thereof, theinterior of the motor is not contaminated by dust, so labor therefor canbe saved by omitting the disassembly of the electric motors for cleaningthe insides thereof.

However, since the bearings are lubricated by grease filled in bearingportions, the lubricant grease deteriorated by the operation, and thelubricant grease needs to be renewed. The renewal of the lubricantgrease needs to be performed after having disassembled the electricmotors, by which large amounts of labor and time were required.

For example, a rotor suspending jig is set to each shaft end of therotor shaft, and after having detached the bracket and the housing fromthe frame, an entirety of the rotor in a state of still having thebearings attached is drawn out from the frame in an axial direction.Thereafter, the bracket and the housing are drawn out from the rotor,and the grease of the bearing portions is replaced with a new one. Afterreplacing the grease, the rotor is inserted into the frame in anopposite order and is coaxially aligned, and thus the electric motor isreassembled.

As aforementioned, although the cleaning of the inside due tocontamination becomes unnecessary by forming the electric motors as thefully enclosed type, the disassembly and reassembly of the electricmotors need to be performed periodically in order to renew the bearinglubricant grease, and this is requiring large amounts of labor and time.Further, replacements of the bearings become necessary due to long-termuse, wear, and the like, and at such occasions, the electric motors needto be disassembled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing an electric motor of a firstembodiment.

FIG. 2 is a front view of the electric motor of the first embodiment.

FIG. 3 is a cross sectional view of the electric motor showing a processof disassembling the electric motor of the first embodiment.

FIG. 4 is a cross sectional view showing a part of an electric motor ofa second embodiment.

FIG. 5 is a cross sectional view showing a part of an electric motor ofa third embodiment.

FIG. 6 is a front view showing a separating plate of the electric motorof the third embodiment.

FIG. 7 is a side view partially showing a separating plate and a fixingbold of an electric motor of a fourth embodiment.

FIG. 8 is a cross sectional view showing an electric motor of a fifthembodiment.

FIG. 9 is a cross sectional view showing an electric motor of a sixthembodiment.

FIG. 10 is a side view of a railway vehicle having electric motors.

DETAILED DESCRIPTION

In general, according to one embodiment, an electric motor comprises astator, a rotor, bearings and a rotor shaft, in a frame; supportingsurfaces on the rotor; and a plurality of threaded holes in the frame,configured to receive bolts for pressing the support surfaces fromoutside.

An electric motor for driving a vehicle according to various embodimentswill be described in detail with reference to the drawings.

Firstly, a railway vehicle comprising electric motors will be explained.FIG. 10 schematically shows the railway vehicle. This railway vehicle 60includes a pair of truck frames 52 in each of which wheels 50 areprovided, and a vehicle body 55 supported via air springs 54 on thetruck frames. On each truck frame 52 and near the wheels 50, electricmotors 10 that function as traction electric motors are mounted. Theelectric motors 10 are connected so as to be capable of transmitting therotation force to the wheels 50 via couplings and gear boxes not shown.The wheels 50 are mounted on rails not shown. A structure configured ofthe wheels 50, the truck frames 52, and the air springs 54 willcollectively be termed a truck.

Pantographs 57 are provided on a ceiling slide of the vehicle body 55,and these pantographs are in contact with an overhead power line 58.Electric power supplied from the overhead power line 58 to thepantographs 57 is supplied to a controlling device not shown. Theelectric power is converted from direct current to alternating currentby the controlling device, and is supplied to respective electric motors10 through wirings not shown. The electric motors 10 operate by usingthe supplied electric power, and rotate the wheels 50 via the couplingsand the gear boxes. Due to this, the vehicle body 55 runs on the rails.

Next, the electric motors according to the embodiments will beexplained.

First Embodiment

FIG. 1 is a longitudinal cross sectional view showing a fully enclosedtype electric motor according to the first embodiment, and FIG. 2 is afront view showing a driving side of the electric motor. As shown inFIG. 1 and FIG. 2, the electric motor 10 includes a cylindrical frame17. One end of the frame 17 in an axial direction is closed by anannular end plate 16, and the other end of the frame 17 in the axialdirection is closed by an annular bracket 19 bolt-fixed to the frame.The end plate 16 is integrally formed with the frame 17. A case (devicebody) whose inside is sealed is configured by these frame 17, end plate16, and bracket 19.

A cylindrical stator core 2 is fixed concentrically with the frame 17 onan inner circumferential surface of the frame 17. A pair of annular coreholders 4 a and 4 b is fixed to both end surfaces of the stator core 2.The stator core 2 is configured by stacking a plural of annular metalplates made of a ferromagnetic material, for example, silicon steelplates. A plurality of slots extending respectively in the axialdirection are formed at an inner circumferential portion of the statorcore 2, and stator coils 3 are embedded in these slots. Coil ends of thestator coils 3 project in the axial direction from the both end surfacesof the stator core 2. The stator core 2 and stator coils 3 constitute astator (stationary part).

An opening is formed at a center portion of the bracket 19, and a firstbearing housing 21 is fitted into this opening from outside. A flangeportion 21 a of the first bearing housing 21 is bolt-fixed to an outersurface of the bracket 19 by a plurality of bolts 25 from the outside,and due to this, the first bearing housing 21 is fixed to the bracket19. A first bearing 6 is internally provided in the first bearinghousing 21. A lubricant grease is filled in the first bearing 6.

An opening is formed at a center portion of the end plate 16 of theframe 17, and a second bearing housing 22 is fitted into this openingfrom the outside. A flange portion 22 a of the second bearing housing 22is bolt-fixed to the outer surface of the end plate 16 by a plurality ofbolts 26 from the outside, and due to this, the second bearing housing22 is fixed to the end plate 16. A second bearing 7 is internallyprovided in the second bearing housing 22. A lubricant grease is filledin the second bearing 7.

A columnar rotor core 9 is arranged inside the stator core 2 coaxiallywith the stator core with a space therebetween. A rotor shaft 8 isattached to a center portion of the rotor core 9 configuring a rotor,and both axial end portions of the rotor shaft 8 are rotatably supportedby the first bearing 6 and the second bearing 7. An outer race of thefirst bearing 6 fits with an inner circumference of the first bearinghousing 21, and an inner race thereof fits with an outer circumferenceof the rotor shaft 8. An outer race of the second bearing 7 fits with aninner circumference of the second bearing housing 22, and an inner racethereof fits with the outer circumference of the rotor shaft 8. Due tothis, the rotor shaft 8 extends coaxially in the case. A driving sideend portion 8 a of the rotor shaft 8 extends to outside the device, anda joint for connecting a driving gear device is attached to the endportion.

The rotor core 9 is configured by stacking a plural of annular metalplates made of a ferromagnetic material, for example, silicon steelplates. The rotor core 9 is supported and sandwiched from both sides inthe axial direction by a pair of core holders 11 a and 11 b attached tothe rotor shaft 8. The core holder 11 a and 11 b are arranged annularly,and the outer diameter thereof is formed slightly smaller than the outerdiameter of the rotor core 9.

A plurality of grooves respectively extending in the axial direction isformed on an outer circumferential portion of the rotor core 9, and arotor bar 30 is embedded in each groove. Both end portions of therespective rotor bars 30 extend outside from the rotor core 9, and abasket-shaped rotor of the induction electric motor is formed byintegrally connecting the extended portions by an end ring. Byelectrically conducting the stator coil 3, the rotor core 9 is inductedand rotated, and the rotor shaft 8 is rotated together with the rotorcore 9.

A first separating plate 23 is attached to the rotor shaft 8 coaxiallybetween the first bearing 6 and the rotor core 9, and is configuredintegrally rotatable with the rotor shaft 8. The first separating plate23 is formed in a substantially funnel shape, and extends tiltingly froma rotor core 9 side toward the bracket 19. An outer circumferential edgeportion of the first separating plate 23 and an inner circumferentialportion of an extended portion of the bracket 19 on a device inner sideare engaged with one another with a minute annular space therebetween.This minute annular space portion is formed in a two-layer structurehaving a concavo-convex shape, and forms a labyrinth structure portion15 a.

A second separating plate 24 is coaxially attached to the rotor shaft 8between the second bearing 7 and the rotor core 9, and is configuredintegrally rotatable with the rotor shaft 8. The second separating plate24 is formed in a substantially funnel shape, and extends tiltingly fromthe rotor core 9 side toward the end plate 16. An outer circumferentialedge portion of the second separating plate 24 and an innercircumferential portion of an extended portion of the end plate 16 onthe device inner side are engaged with one another with a minute annularspace therebetween. This minute annular space portion is formed in atwo-layer structure having a concavo-convex shape, and forms a labyrinthstructure portion 15 b.

The first separating plate 23 and the second separating plate 24 form asealed space 14 inside the case via the labyrinth structure portions 15a and 15 b. The stator core 2 and the rotor core 9 are arranged insidethe sealed space 14.

As shown in FIG. 1 and FIG. 2, an annular external air flowing space 12coaxial with the rotor shaft 8 is formed between the first separatingplate 23, the bracket 19, and the first bearing housing 21, and theexternal air flowing space 12 communicates with a space outside thedevice through a plurality of ventilating openings 19 a provided in thebracket 19. An annular external air flowing space 13 coaxial with therotor shaft 8 is formed between the second separating plate 24, the endplate 16, and the second bearing housing 22, and the external airflowing space 13 communicates with the space outside the device thorougha plurality of ventilating openings 17 a provided in the end plate 16.

A supporting surface for supporting the rotor is formed on at least apart of a supporting body that is fixed to the rotor shaft 8 and rotatesintegrally with the rotor core 9. In the present embodiment, the firstseparating plate 23 and the second separating plate 24 respectivelyconfigure the supporting body. A tapered surface 23 a having the rotorshaft 8 as a center is formed at least at a part of a side surface on anoutside of the first separating plate 23. This tapered surface 23 aconfigures a supporting surface. In the present embodiment, although thetapered surface 23 a is formed continuingly at an entire circumferencein a circumferential direction, it may be formed at least at a partalong the circumferential direction, or be intermittently formed atplural parts along the circumferential direction. As shown in FIG. 1 andFIG. 2, in the first bracket 19, a plurality, for example, 5 pieces ofthreaded holes 20 for fixing are provided at positions opposing thetapered surface 23 a of the first separating plate 23 in a mannerpenetrating in the axial direction. These threaded holes 20 for fixingare provided to align on a circumference having the rotor shaft 8 as acenter. The threaded holes 20 for fixing are provided at three positionson an upper half side than the axial center on the circumference, andtwo positions on a lower half side.

A tapered surface 24 a having the rotor shaft 8 as a center is formed ata side surface on an outside of the second separating plate 24, and thistapered surface 24 a configures a supporting surface. In the end plate16, a plurality, for example, 5 pieces of threaded holes 18 for fixingare provided at positions opposing the tapered surface 24 a in a mannerpenetrating in the axial direction. These threaded holes 18 for fixingare provided to align on the circumference having the rotor shaft 8 asthe center. The threaded holes 18 for fixing are provided at threepositions on the upper half side than the axial center on thecircumference, and two positions on the lower half side. Note that thesethreaded holes 18 and 20 for fixing are not limited to five pieces, butmay be increased or decreased in accordance with needs. Further, formingpositions of the threaded holes for fixing may be at equal intervals inthe circumferential direction, or may be at unequal intervalstherealong.

Bolts 27 and 28 for fixing the rotor can respectively be screwed intothe threaded holes 18 and 20 for fixing. The entirety of the rotor canbe fixed to and supported on the case by screwing the bolts 27 and 28into the threaded holes 18 and 20 for fixing, and pressing tip ends ofthe bolts 27 and 28 against the tapered surface 23 a of the firstseparating plate 23 and the tapered surface 24 a of the secondseparating plate 24.

Normally (during an operation of the electric motor), the bolts 27 and28 for fixing are detached from the bracket 19 and the end plate 16.Alternately, the bolts 27 and 28 may be attached to the case in a stateof being screwed in the threaded holes 18 and 20 for fixing withouthaving the tip ends thereof make contact with the first and secondseparating plates 23 and 24. Further, normally (during the operation ofthe electric motor), dummy bolts that are much shorter than the bolts 27and 28 may be screwed in the threaded holes 20 and 18 for fixing so asto protect the threaded holes for fixing and to prevent dust fromentering from the threaded holes.

As shown in FIG. 2, the electric motor 10 is attached to the truck byfixing supporting arms 5 a and 5 b provided on the outer circumferentialportion of the frame 17 to the truck frame 52. Further, the driving sideend portion 8 a of the rotor shaft 8 is coupled to the driving geardevice by a joint.

Next, there will now be described summaries of performing renewal of thebearing lubricant grease of the electric motor 10 configured asdescribed above and replacement of the bearings. As shown in FIG. 3,firstly, the bolts 27 for fixing the rotor are screwed into theplurality of threaded holes 20 for fixing provided in the bracket 19,and the tapered surface 23 a formed on the first separating plate 23 ispressed by the bolts 27. At the same time, the bolts 28 for fixing therotor are screwed into the plurality of threaded holes 18 for fixingprovided in the end plate 16, and the tapered surface 24 a formed on thesecond separating plate 24 is pressed by the bolts 28. By tightening thefirst separating plate 23 and the second separating plate 24 that areintegral with the rotor from both sides in the axial direction by thebolts 27 and 28, the rotor is fixed to the case at its correct position,that is, by being positioned coaxially with the stator core 2, andretained at predetermined positions with respect to the axial directionof the stator.

Then, after having taken the bolt 25 off, the first bearing housing 21is drawn out toward outside from the bracket 19, and the lubricantgrease of the bearing outer race 6 a attached to the inner circumferenceof the first bearing housing 21 is replaced with a new one. Similarly,the bolt 26 is taken off and the second bearing housing 22 is drawn outtoward outside from the end plate 16, and the lubricant grease of thebearing outer race 7 b attached to the inner circumference of the secondbearing housing 22 is replaced with a new one. At this occasion, sincethe entirety of the rotor including the rotor shaft 8 is fixed andretained by the bolts 27 and 28, the entirety of the rotor is retainedat the predetermined position with respect to the stator even when thefirst bearing housing 21 and the second bearing housing 22 are drawnout.

After having renewed the bearing grease, the first bearing housing 21and the second bearing housing 22 are assembled to the bracket 19 andthe end plate 16, and are fixed to the bracket 19 and the end plate bythe bolts 25 and 26. Next, by taking the bolts 27 and 28 for fixing therotor off from the case, or by loosening the same to the positions bywhich no contact is made with the first separating plate 23 and thesecond separating plate 24, the renewal of the lubricant grease iscompleted.

Further, the replacement of the bearings 6 and 7 can be performed in thesame order as the above; after having disassembled the electric motor 10as shown in FIG. 3, the bearing outer race 6 a is detached from thefirst bearing housing 21 and a new bearing outer race is attached.Similarly, the bearing outer race 7 a is detached from the secondbearing housing 22 and a new bearing outer race is attached. Bearinginner races 6 b and 7 b attached to the rotor shaft 8 are detached fromthe rotor shaft 8 by using a jig, and thereafter new bearing inner racesare attached to the rotor shaft 8.

Note that, in order to press the tapered surfaces 23 a and 24 a of therotor to position the rotor at the correct position, preferably, threeor more pieces of the bolts 27 and 28 for fixing the rotor may beprovided on each side, and they may be provided at positions dispersedon the upper half side and the lower half side than the axial center onthe circumference. In the present embodiment, three pieces are providedon the upper half and two pieces are provided on the lower half, and anumber of the bolts on the upper half burdened with the weight of therotor is made larger than that of the lower half.

In the electric motor 10 configured as above of the present embodiment,the renewal of the lubricant grease of the bearings and the replacementof the bearings can be performed without performing disassembly theelectric motor in which the rotor has to be drawn out. Due to this,labor-saving for maintenance of the electric motor 10 can be achieved.The rotor can be retained at the predetermined position with respect tothe stator, that is, at the predetermined position coaxially with thepredetermined space and along the axial direction by the bolts forfixing the rotor. Due to this, positional displacement of the rotorcaused by disassembling the bearing can be prevented, and operabilitycan be improved, for a positional adjustment of the rotor uponreassembling the bearings becomes unnecessary.

Second Embodiment

Next, an electric motor according to the second embodiment will beexplained. In the second embodiment, portions identical to those of thefirst embodiment will be given the same reference signs, and detailedexplanations thereof will be omitted, and configurations that differfrom the first embodiment will be explained in detail.

FIG. 4 is a longitudinal cross sectional view showing a part of a fullyenclosed type electric motor of the second embodiment. As shown in FIG.4, a bracket 19 is fixed to a driving side end of a frame 17, and afirst bearing housing 21 in which a first bearing 6 is internallyprovided is attached on an inner circumferential side of the bracket 19.One end of a rotor shaft 8 is supported by the first bearing 6.

A first separating plate 23 is fixed to the rotor shaft 8 at one endside of a rotor core 9. A labyrinth structure configured of a minuteannular space is formed between an outer circumferential portion sidesurface of the first separating plate 23 and the bracket 19.

A tapered surface 23 a having the rotor shaft 8 as a center is formed onan outer circumferential surface of the first separating plate 23. Aplurality of threaded holes 20 for fixing is provided on a circumferenceon a side surface of the bracket 19 at positions opposing the outercircumferential surface of the first separating plate 23. Each of thethreaded holes 20 for fixing is formed to penetrate at an anglesubstantially perpendicular to the tapered surface 23 a of the firstseparating plate 23.

The other end side of the rotor shaft 8 (opposite to a driving side) hassimilar configuration as the above driving side, or may have similarconfiguration as a side opposite to a driving side in the firstembodiment.

According to the electric motor 10 configured as above, the rotor can befixed and retained at a correct position by screwing the bolts 27 forfixing the rotor in the threaded holes 20 for fixing, and pressing thetapered surface 23 a of the first separating plate 23. Since the rotorcan be fixed by bolts for fixing even when bearings are taken off,renewal of a lubricant grease and replacement of the bearings can beperformed without disassembling the electric motor at a large scale, assimilar to the first embodiment.

Further, in the second embodiment, since the bolts 27 are pressedagainst the tapered surface 23 a substantially perpendicular thereto, abending force is not exerted on the bolts 27, so a size of the bolts canbe made small. That is, even in the case of using bolts of a smallersize, the rotor can stably be fixed and retained. Further, since asurface pressure on the tapered surface of the first separating platecan be reduced, a surface will not be dented by the pressure even if amaterial of the first separating plate 23 has a relatively low hardnesssuch as aluminum alloy.

Third Embodiment

Next, an electric motor according to the third embodiment will beexplained. In the third embodiment, portions identical to those of thefirst embodiment will be given the same reference signs, and detailedexplanations thereof will be omitted, and configurations that differfrom the first embodiment will be explained in detail.

FIG. 5 is a longitudinal cross sectional view showing a part of a fullyenclosed type electric motor of the third embodiment, and FIG. 6 is afront view showing a side surface on an outside of a first separatingplate. As shown in FIG. 5 and FIG. 6, a plurality of fins 34 and 35 isprovided on a side surface on an outside of a first separating plate 23attached to a rotor shaft 8. The fins 34 and 35 are arranged radiatinglywith the rotor shaft 8 as a center, and are arranged alternately along acircumferential direction.

The plurality of fins 34 have tapered surfaces 34 a having the rotorshaft 8 as a center. These tapered surfaces 23 a configure supportingsurfaces. A plurality of threaded holes 20 for fixing is formed atpositions opposing the fins 34 on a side surface of a bracket 19, eachof which penetrates the bracket in an axial direction. The plurality ofthreaded holes 20 for fixing is arranged aligning on a circumferencehaving the rotor shaft 8 as a center. Further, the threaded holes 20 forfixing are arranged at positions on the same circumference as thetapered surfaces 34 a of the fins 34 at substantially the same diameter.

The other end side of the rotor shaft (opposite to a driving side) hassimilar configuration as the above driving side, or may have similarconfiguration as a side opposite to a driving side in the firstembodiment.

In an electric motor 10 configured as above, upon operation, flow ofexternal air increases due to a fan effect of the fins 34 and 35 causedby a rotation of the first separating plate 23, and cooling effect isincreased. At the same time, since a heat dissipating area of the firstseparating plate 23 is increased by the fins 34 and 35, cooling effectof a rotor further increases.

In cases of performing renewal of a bearing grease or replacement ofbearings, the rotor can be fixed and retained by screwing bolts 27 forfixing the rotor in the threaded holes 20 for fixing, and pressing thetapered surfaces 34 a of the fins 34. Due to this, a first bearinghousing 21 and a second bearing housing can be drawn out without drawingthe rotor out.

Since the fins 34 having the tapered surfaces 34 a are arranged on thefirst separating plate 23 so as to correspond to the positions of theplurality of threaded holes 20 for fixing on the circumference providedon the bracket 19, the rotor can be fixed by the bolts 27 without anyproblem. Due to this, similar effects as that of the first embodimentcan be achieved.

Fourth Embodiment

Next, a bolt for fixing a rotor in an electric motor of the fourthembodiment will be explained. In the fourth embodiment, portionsidentical to those of the first embodiment will be given the samereference signs, and detailed explanations thereof will be omitted, andconfigurations that differ from the first embodiment will be explainedin detail.

FIG. 7 shows the bolt for fixing the rotor and a first separating plate23 of the electric motor of the fourth embodiment. A tapered surface 27a with an angle θ is formed at a tip end portion of the bolt 27. Thetaper angle θ of this tapered surface 27 a is set to be identical to ataper angle θ of a tapered surface 23 a formed on the first separatingplate 23 on a rotor side.

When such a bolt 27 for fixing the rotor is pressed against the taperedsurface 23 a of the first separating plate 23, a contacting position ofthe bolt 27 and the tapered surface 23 a is enlarged from a point to aline. Due to this, a position of a rotor can further be retainedcorrectly. Further, since a surface pressure on contacting surfaces isreduced, dents caused by pressure, and the like can be prevented frombeing generated on the tapered surface.

Fifth Embodiment

Next, an electric motor of the fifth embodiment will be explained. Inthe fifth embodiment, portions identical to those of the firstembodiment will be given the same reference signs, and detailedexplanations thereof will be omitted, and configurations that differfrom the first embodiment will be explained in detail.

FIG. 8 is a longitudinal cross sectional view showing a part of a fullyenclosed type electric motor of the fifth embodiment. As shown in FIG.8, a bracket 19 is fixed at a driving side end of a frame 17, and afirst bearing housing 21 in which a first bearing 6 is internallyprovided is fixed by a bolt 25 at an inner circumferential side of thebracket 19. An end on a side opposite to the driving side end of theframe 17 is closed by an end plate 16. A second bearing housing 22 inwhich a second bearing 7 is internally provided is fixed by a bolt 26 ata center portion of the end plate. A rotor shaft 8 of a rotor isarranged in a case, and both end portions of the rotor shaft 8 arerotatably supported by the first bearing 6 and the second bearing 7.

In the fifth embodiment, a first separating plate and a secondseparating plate are not provided, and the case is formed as a sealedcasing. A rotor core 9 and a pair of core holders 11 a and 11 b areattached to the rotor shaft 8. These core holders 11 a and 11 b arefixed to the rotor shaft 8, and configure a supporting body thatintegrally rotates with the rotor. Tapered surfaces 36 a and 36 b havingthe rotor shaft 8 as a center are respectively formed on outercircumferential surfaces of the core holders 11 a and 11 b. Thesetapered surfaces 36 a and 36 b configure a supporting surface.

In the bracket 19, a plurality of threaded holes 20 for fixing isprovided at positions opposing the tapered surface 36 a of the coreholder 11 a. These threaded holes 20 for fixing are provided to align ona circumference having the rotor shaft 8 as a center. Each of thethreaded holes 20 for fixing is formed in a manner penetrating in adirection substantially perpendicular to the tapered surface 36 a.Further, bolts 27 for fixing the rotor are configured to be capable ofbeing screwed in the respective threaded holes 20 for fixing from anoutside.

In the end plate 16, a plurality of threaded holes 18 for fixing isprovided at positions opposing the tapered surface 36 b of the coreholder 11 b. These threaded holes 18 for fixing are provided to align ona circumference having the rotor shaft 8 as a center. Each of thethreaded holes 18 for fixing is formed in a manner penetrating in adirection substantially perpendicular to the tapered surface 36 b.Further, bolts 28 for fixing the rotor are configured to be capable ofbeing screwed in the respective threaded holes 18 for fixing from anoutside.

According to an electric motor 10 configured as above, the rotor can befixed and retained at a correct position by screwing the bolts 27 forfixing the rotor in the threaded holes 20 for fixing and therebypressing the tapered surface 36 a of the core holder 11 a, and screwingthe bolts 28 for fixing the rotor in the threaded holes 18 for fixingand thereby pressing the tapered surface 36 b of the core holder 11 b.Since the rotor can be fixed to a stator by the bolts 27 and 28 evenwhen the first and second bearing housings 21 and 22 and the first andsecond bearings 6 and 7 are detached from the rotor shaft 8, renewal ofa lubricant grease and replacement of bearings can be performed withoutdisassembling the electric motor at a large scale, as similar to thefirst embodiment. Due to this, labor-saving for maintenance of theelectric motor 10 can be achieved.

Further, in the fifth embodiment, since the bolts 27 and 28 are pressedagainst the tapered surfaces 36 a and 36 b at substantiallyperpendicular thereto, a bending force is not exerted on the bolts 27and 28, so that sizes of the bolts can be made small. That is, even inthe case of using bolts of smaller sizes, the rotor can stably be fixedand retained. Further, since surface pressures on the tapered surfacesof the core holders 11 a and 11 b can be reduced, surfaces will not bedented by the pressures even if materials of core holders have arelatively low hardness as in aluminum alloy and the like.

Sixth Embodiment

Next, an electric motor of the sixth embodiment will be explained.Although the first to fifth embodiments as explained above haveexplained about the fully enclosed type electric motors, the presentinvention is not limited to the fully enclosed type, and may be appliedto an open-type self-ventilation cooling scheme electric motor.

The sixth embodiment shows the open-type self-ventilation cooling schemeelectric motor. Note that, in the sixth embodiment, portions identicalto those of the first embodiment will be given the same reference signs,and detailed explanations thereof will be omitted, and configurationsthat differ from the first embodiment will be explained in detail.

FIG. 9 is a longitudinal cross sectional view showing the electric motorof the sixth embodiment. As shown in the drawing, a bracket 19 is fixedto a driving side end of a cylindrical frame 17, and a first bearinghousing 21 in which a first bearing 6 is internally provided is attachedby a bolt 25 at an inner circumferential side of the bracket 19. A sideopposite to the driving side of the frame 17 is closed by an end plate16. A second bearing housing 22 in which a second bearing 7 isinternally provided is attached by a bolt 26 at a center portion of theend plate 16.

A rotor shaft 8 of a rotor is arranged in a case, and both end portionsof the rotor shaft 8 are rotatably supported by the first bearing 6 andthe second bearing 7. A rotor core 9 and a pair of core holders 11 a and11 b are attached to the rotor shaft 8. A plurality of ventilation holes9 a respectively extending penetratingly in an axial direction is formedon the rotor core 9. A cylindrical stator core 2 is fixed to an innercircumferential surface of a frame 17, and is positioned coaxially withthe rotor core 9 at an outer circumference thereof.

A ventilating fan 40 is attached to an end portion on a driving side ofthe rotor shaft 8, and is configured to be capable of integrallyrotating with the rotor. The ventilating fan 40 configures a supportingbody of the present invention. A tapered surface 40 a having the rotorshaft 8 as a center is formed at a side surface facing outward from theventilating fan 40, that is, a side surface opposing the bracket 19.

A funnel-shaped supporting body 42 is attached to an end portion on aside opposite to the driving side of the rotor shaft 8, and isconfigured to be capable of integrally rotating with the rotor. Atapered surface 42 a having the rotor shaft 8 as a center is formed at aside surface facing outward from the supporting body 42, that is, a sidesurface opposing the end plate 16.

These tapered surfaces 40 a and 42 a are fixed to the rotor shaft 8, andconfigure a supporting surface formed on the supporting body thatintegrally rotates with the rotor.

In the bracket 19, a plurality of threaded holes 20 for fixing isprovided at positions opposing the tapered surface 40 a of theventilating fan 40. These threaded holes 20 for fixing are provided toalign on a circumference having the rotor shaft 8 as a center. Each ofthe threaded holes 20 for fixing is formed, for example, in a mannerpenetrating in an axial direction of a case. Further, bolts 27 forfixing the rotor are configured to be capable of being screwed in therespective threaded holes 20 for fixing from an outside.

In the end plate 16, a plurality of threaded holes 18 for fixing isprovided at positions opposing the tapered surface 42 a of thesupporting body 42. These threaded holes 18 for fixing are provided toalign on a circumference having the rotor shaft 8 as a center. Each ofthe threaded holes 18 for fixing is formed, for example, in a mannerpenetrating in the axial direction of the case. Further, bolts 28 forfixing the rotor are configured to be capable of being screwed in therespective threaded holes 18 for fixing from an outside.

In the bracket 19, a plurality of air discharging openings 44 is formedat positions opposing an outer circumferential portion of theventilating fan 40. An air intaking opening 46 is formed at an endportion on a side opposite to the driving side of the frame 17.

During an operation of the electric motor, the ventilating fan 40rotates integrally with the rotor. External air flows into the insidefrom the air intaking opening 46 of the frame 17 by the rotation of theventilating fan 40, flows to the driving side through the ventilationholes 9 a of the rotor core 9 and the space between the rotor core 9 andthe stator core 2, and flows out to the outside from the air dischargingopenings 44 of the bracket 19 after having cooled the same.

According to the electric motor configured as above, the rotor can befixed and retained at a correct position by screwing the bolts 27 forfixing the rotor in the threaded holes 20 for fixing and therebypressing the tapered surface 40 a of the ventilating fan 40, andscrewing the bolts 28 for fixing the rotor in the threaded holes 18 forfixing and thereby pressing the tapered surface 42 a of the supportingbody 42. Since the rotor can be fixed to a stator by the bolts 27 and 28even when the first and second bearing housings 21 and 22 and the firstand second bearings 6 and 7 are detached from the rotor shaft 8, renewalof a lubricant grease and replacement of bearings can be performedwithout disassembling the electric motor at a large scale, as similar tothe first embodiment. Due to this, labor-saving for maintenance of theself-ventilation cooling type electric motor can be achieved.

Note that the present invention is not limited to the embodimentsdescribed above, and upon implications, various modifications can bemade thereto within a scope that does not go beyond an essence thereof.Further, the embodiments as above includes inventions at various stages,various inventions may be extracted therefrom according to appropriatecombinations of a plurality of constituent features as disclosed. Forexample, even if some of the constituent features are deleted from anentirety of the constituent features shown in the embodiments, if theproblem as described in the section of the technical problem can besolved, and the effect as described in the section of the advantageouseffects of the invention can be achieved, the configuration in whichthese constituent features are deleted may be extracted as an invention.

This invention may be applied not only to electromagnetic inductionmotors, but also to magnetic motors. The numbers of the threaded holesfor fixing and the bolts are not limited to the embodiments, and may beincreased or decreased as needed.

What is claimed is:
 1. An electric motor comprising: a stator, a rotor,bearings and a rotor shaft in a frame; supporting surfaces on the rotor;and a plurality of threaded holes in the frame, which are configured toreceive bolts for pressing the support surfaces from outside.
 2. Anelectric motor according to claim 1, wherein the rotor comprises a rotorcore attached to the rotor shaft, and rotor holders attached to therotor shaft at respective sides of the rotor core and respectivelyincluding the supporting surfaces.
 3. An electric motor according toclaim 1, wherein the rotor comprises a rotor core attached to the rotorshaft, and a first separating plate and a second separating plateattached to the rotor shaft and respectively comprising the supportingsurfaces.
 4. An electric motor according to claim 1, wherein the rotorcomprises a rotor core attached to the rotor shaft, and a ventilatingfan and a supporting body attached to the rotor shaft at respectivesides of the rotor core and respectively comprising the supportingsurfaces.
 5. An electric motor comprising: a frame supporting a stator;a bracket and an end plate configured to close respective ends of theframe; a first bearing housing and a second bearing housing respectivelyretaining bearings, and respectively fixed to the bracket and the endplate from an outside; a rotor shaft arranged inside the frame androtatably supported by the bearings; a rotor attached to the rotor shaftand opposing the stator; supporting surfaces on the rotor; a pluralityof threaded holes formed respectively in the bracket and the end plateto oppose the supporting surfaces, and configured to receive bolts forpressing the support surfaces from outside.
 6. An electric motoraccording to claim 5, wherein the rotor comprises a rotor core attachedto the rotor shaft, and rotor holders attached to the rotor shaft atrespective sides of the rotor core and respectively including thesupporting surfaces.
 7. The electric motor according to claim 6, whereinthe supporting surfaces of the core holders comprise tapered surfacespositioned at least at parts on a circumference having the rotor shaftas a center, and the plurality of threaded holes are formed in thebracket and the end plate so as to align on circumferences having therotor shaft as centers.
 8. An electric motor according to claim 5,wherein the rotor comprising a rotor core attached to the rotor shaft,and a first separating plate and a second separating plate attached tothe rotor shaft at respective sides of the rotor core and respectivelyincluding the supporting surfaces.
 9. The electric motor according toclaim 8, wherein the supporting surfaces of the first and secondseparating plates comprise tapered surfaces positioned at least at partson a circumference having the rotor shaft as a center, and the pluralityof threaded holes are formed in the bracket and the end plate so as toalign on circumferences having the rotor shaft as centers.
 10. Theelectric motor according to claim 9, wherein annular labyrinths areformed between an outer circumferential portion of the first separatingplate and the bracket, and between an outer circumferential portion ofthe second separating plate and the end plate, respectively.
 11. Theelectric motor according to claim 9, wherein the first separating plateand the second separating plate respectively comprise side surfacesfacing the outside, and the tapered surfaces are formed on these sidesurfaces.
 12. The electric motor according to claim 9, wherein thetapered surface is formed on an outer circumferential portion of thefirst separating plate, and the plurality of threaded holes for fixingis respectively formed to penetrate in a direction substantiallyperpendicular to the tapered surface.
 13. The electric motor accordingto claim 9, wherein the first separating plate comprises a side surfacefacing the outside, and a plurality of fins formed on the side surfaceand extending radially with the rotor shaft as a center, and the taperedsurfaces are formed on the fins.
 14. An electric motor according toclaim 5, wherein the rotor comprising a rotor core attached to the rotorshaft, and a ventilating fan and a supporting body attached to the rotorshaft at respective sides of the rotor core and respectively comprisingthe supporting surfaces.
 15. The electric motor according to claim 14,wherein the supporting surfaces of the ventilating fan and thesupporting body comprise tapered surfaces that are positioned at leastat parts on circumferences having the rotor shaft as centers, and theplurality of threaded holes for fixing are formed in the bracket and theend plate to align on circumferences having the rotor shaft as centers.16. The electric motor according to claim 15, wherein the bolts forpressing the rotor comprise tapered surfaces formed at tip end portionsthereof, and the tapered surfaces have a substantially identical taperangle as the tapered surface formed on the supporting body.